/*
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 */

package java.lang;

import sun.misc.FloatingDecimal;
import sun.misc.FpUtils;
import sun.misc.DoubleConsts;

/**
 * The {@code Double} class wraps a value of the primitive type
 * {@code double} in an object. An object of type
 * {@code Double} contains a single field whose type is
 * {@code double}.
 *
 * <p>In addition, this class provides several methods for converting a
 * {@code double} to a {@code String} and a
 * {@code String} to a {@code double}, as well as other
 * constants and methods useful when dealing with a
 * {@code double}.
 *
 * @author Lee Boynton
 * @author Arthur van Hoff
 * @author Joseph D. Darcy
 * @since JDK1.0
 */
public final class Double extends Number implements Comparable<Double> {

  /**
   * A constant holding the positive infinity of type
   * {@code double}. It is equal to the value returned by
   * {@code Double.longBitsToDouble(0x7ff0000000000000L)}.
   */
  public static final double POSITIVE_INFINITY = 1.0 / 0.0;

  /**
   * A constant holding the negative infinity of type
   * {@code double}. It is equal to the value returned by
   * {@code Double.longBitsToDouble(0xfff0000000000000L)}.
   */
  public static final double NEGATIVE_INFINITY = -1.0 / 0.0;

  /**
   * A constant holding a Not-a-Number (NaN) value of type
   * {@code double}. It is equivalent to the value returned by
   * {@code Double.longBitsToDouble(0x7ff8000000000000L)}.
   */
  public static final double NaN = 0.0d / 0.0;

  /**
   * A constant holding the largest positive finite value of type
   * {@code double},
   * (2-2<sup>-52</sup>)&middot;2<sup>1023</sup>.  It is equal to
   * the hexadecimal floating-point literal
   * {@code 0x1.fffffffffffffP+1023} and also equal to
   * {@code Double.longBitsToDouble(0x7fefffffffffffffL)}.
   */
  public static final double MAX_VALUE = 0x1.fffffffffffffP+1023; // 1.7976931348623157e+308

  /**
   * A constant holding the smallest positive normal value of type
   * {@code double}, 2<sup>-1022</sup>.  It is equal to the
   * hexadecimal floating-point literal {@code 0x1.0p-1022} and also
   * equal to {@code Double.longBitsToDouble(0x0010000000000000L)}.
   *
   * @since 1.6
   */
  public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308

  /**
   * A constant holding the smallest positive nonzero value of type
   * {@code double}, 2<sup>-1074</sup>. It is equal to the
   * hexadecimal floating-point literal
   * {@code 0x0.0000000000001P-1022} and also equal to
   * {@code Double.longBitsToDouble(0x1L)}.
   */
  public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324

  /**
   * Maximum exponent a finite {@code double} variable may have.
   * It is equal to the value returned by
   * {@code Math.getExponent(Double.MAX_VALUE)}.
   *
   * @since 1.6
   */
  public static final int MAX_EXPONENT = 1023;

  /**
   * Minimum exponent a normalized {@code double} variable may
   * have.  It is equal to the value returned by
   * {@code Math.getExponent(Double.MIN_NORMAL)}.
   *
   * @since 1.6
   */
  public static final int MIN_EXPONENT = -1022;

  /**
   * The number of bits used to represent a {@code double} value.
   *
   * @since 1.5
   */
  public static final int SIZE = 64;

  /**
   * The number of bytes used to represent a {@code double} value.
   *
   * @since 1.8
   */
  public static final int BYTES = SIZE / Byte.SIZE;

  /**
   * The {@code Class} instance representing the primitive type
   * {@code double}.
   *
   * @since JDK1.1
   */
  @SuppressWarnings("unchecked")
  public static final Class<Double> TYPE = (Class<Double>) Class.getPrimitiveClass("double");

  /**
   * Returns a string representation of the {@code double}
   * argument. All characters mentioned below are ASCII characters.
   * <ul>
   * <li>If the argument is NaN, the result is the string
   * "{@code NaN}".
   * <li>Otherwise, the result is a string that represents the sign and
   * magnitude (absolute value) of the argument. If the sign is negative,
   * the first character of the result is '{@code -}'
   * ({@code '\u005Cu002D'}); if the sign is positive, no sign character
   * appears in the result. As for the magnitude <i>m</i>:
   * <ul>
   * <li>If <i>m</i> is infinity, it is represented by the characters
   * {@code "Infinity"}; thus, positive infinity produces the result
   * {@code "Infinity"} and negative infinity produces the result
   * {@code "-Infinity"}.
   *
   * <li>If <i>m</i> is zero, it is represented by the characters
   * {@code "0.0"}; thus, negative zero produces the result
   * {@code "-0.0"} and positive zero produces the result
   * {@code "0.0"}.
   *
   * <li>If <i>m</i> is greater than or equal to 10<sup>-3</sup> but less
   * than 10<sup>7</sup>, then it is represented as the integer part of
   * <i>m</i>, in decimal form with no leading zeroes, followed by
   * '{@code .}' ({@code '\u005Cu002E'}), followed by one or
   * more decimal digits representing the fractional part of <i>m</i>.
   *
   * <li>If <i>m</i> is less than 10<sup>-3</sup> or greater than or
   * equal to 10<sup>7</sup>, then it is represented in so-called
   * "computerized scientific notation." Let <i>n</i> be the unique
   * integer such that 10<sup><i>n</i></sup> &le; <i>m</i> {@literal <}
   * 10<sup><i>n</i>+1</sup>; then let <i>a</i> be the
   * mathematically exact quotient of <i>m</i> and
   * 10<sup><i>n</i></sup> so that 1 &le; <i>a</i> {@literal <} 10. The
   * magnitude is then represented as the integer part of <i>a</i>,
   * as a single decimal digit, followed by '{@code .}'
   * ({@code '\u005Cu002E'}), followed by decimal digits
   * representing the fractional part of <i>a</i>, followed by the
   * letter '{@code E}' ({@code '\u005Cu0045'}), followed
   * by a representation of <i>n</i> as a decimal integer, as
   * produced by the method {@link Integer#toString(int)}.
   * </ul>
   * </ul>
   * How many digits must be printed for the fractional part of
   * <i>m</i> or <i>a</i>? There must be at least one digit to represent
   * the fractional part, and beyond that as many, but only as many, more
   * digits as are needed to uniquely distinguish the argument value from
   * adjacent values of type {@code double}. That is, suppose that
   * <i>x</i> is the exact mathematical value represented by the decimal
   * representation produced by this method for a finite nonzero argument
   * <i>d</i>. Then <i>d</i> must be the {@code double} value nearest
   * to <i>x</i>; or if two {@code double} values are equally close
   * to <i>x</i>, then <i>d</i> must be one of them and the least
   * significant bit of the significand of <i>d</i> must be {@code 0}.
   *
   * <p>To create localized string representations of a floating-point
   * value, use subclasses of {@link java.text.NumberFormat}.
   *
   * @param d the {@code double} to be converted.
   * @return a string representation of the argument.
   */
  public static String toString(double d) {
    return FloatingDecimal.toJavaFormatString(d);
  }

  /**
   * Returns a hexadecimal string representation of the
   * {@code double} argument. All characters mentioned below
   * are ASCII characters.
   *
   * <ul>
   * <li>If the argument is NaN, the result is the string
   * "{@code NaN}".
   * <li>Otherwise, the result is a string that represents the sign
   * and magnitude of the argument. If the sign is negative, the
   * first character of the result is '{@code -}'
   * ({@code '\u005Cu002D'}); if the sign is positive, no sign
   * character appears in the result. As for the magnitude <i>m</i>:
   *
   * <ul>
   * <li>If <i>m</i> is infinity, it is represented by the string
   * {@code "Infinity"}; thus, positive infinity produces the
   * result {@code "Infinity"} and negative infinity produces
   * the result {@code "-Infinity"}.
   *
   * <li>If <i>m</i> is zero, it is represented by the string
   * {@code "0x0.0p0"}; thus, negative zero produces the result
   * {@code "-0x0.0p0"} and positive zero produces the result
   * {@code "0x0.0p0"}.
   *
   * <li>If <i>m</i> is a {@code double} value with a
   * normalized representation, substrings are used to represent the
   * significand and exponent fields.  The significand is
   * represented by the characters {@code "0x1."}
   * followed by a lowercase hexadecimal representation of the rest
   * of the significand as a fraction.  Trailing zeros in the
   * hexadecimal representation are removed unless all the digits
   * are zero, in which case a single zero is used. Next, the
   * exponent is represented by {@code "p"} followed
   * by a decimal string of the unbiased exponent as if produced by
   * a call to {@link Integer#toString(int) Integer.toString} on the
   * exponent value.
   *
   * <li>If <i>m</i> is a {@code double} value with a subnormal
   * representation, the significand is represented by the
   * characters {@code "0x0."} followed by a
   * hexadecimal representation of the rest of the significand as a
   * fraction.  Trailing zeros in the hexadecimal representation are
   * removed. Next, the exponent is represented by
   * {@code "p-1022"}.  Note that there must be at
   * least one nonzero digit in a subnormal significand.
   *
   * </ul>
   *
   * </ul>
   *
   * <table border>
   * <caption>Examples</caption>
   * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
   * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
   * <tr><td>{@code -1.0}</td>        <td>{@code -0x1.0p0}</td>
   * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
   * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
   * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
   * <tr><td>{@code 0.25}</td>        <td>{@code 0x1.0p-2}</td>
   * <tr><td>{@code Double.MAX_VALUE}</td>
   * <td>{@code 0x1.fffffffffffffp1023}</td>
   * <tr><td>{@code Minimum Normal Value}</td>
   * <td>{@code 0x1.0p-1022}</td>
   * <tr><td>{@code Maximum Subnormal Value}</td>
   * <td>{@code 0x0.fffffffffffffp-1022}</td>
   * <tr><td>{@code Double.MIN_VALUE}</td>
   * <td>{@code 0x0.0000000000001p-1022}</td>
   * </table>
   *
   * @param d the {@code double} to be converted.
   * @return a hex string representation of the argument.
   * @author Joseph D. Darcy
   * @since 1.5
   */
  public static String toHexString(double d) {
        /*
         * Modeled after the "a" conversion specifier in C99, section
         * 7.19.6.1; however, the output of this method is more
         * tightly specified.
         */
    if (!isFinite(d))
    // For infinity and NaN, use the decimal output.
    {
      return Double.toString(d);
    } else {
      // Initialized to maximum size of output.
      StringBuilder answer = new StringBuilder(24);

      if (Math.copySign(1.0, d) == -1.0)    // value is negative,
      {
        answer.append("-");                  // so append sign info
      }

      answer.append("0x");

      d = Math.abs(d);

      if (d == 0.0) {
        answer.append("0.0p0");
      } else {
        boolean subnormal = (d < DoubleConsts.MIN_NORMAL);

        // Isolate significand bits and OR in a high-order bit
        // so that the string representation has a known
        // length.
        long signifBits = (Double.doubleToLongBits(d)
            & DoubleConsts.SIGNIF_BIT_MASK) |
            0x1000000000000000L;

        // Subnormal values have a 0 implicit bit; normal
        // values have a 1 implicit bit.
        answer.append(subnormal ? "0." : "1.");

        // Isolate the low-order 13 digits of the hex
        // representation.  If all the digits are zero,
        // replace with a single 0; otherwise, remove all
        // trailing zeros.
        String signif = Long.toHexString(signifBits).substring(3, 16);
        answer.append(signif.equals("0000000000000") ? // 13 zeros
            "0" :
            signif.replaceFirst("0{1,12}$", ""));

        answer.append('p');
        // If the value is subnormal, use the E_min exponent
        // value for double; otherwise, extract and report d's
        // exponent (the representation of a subnormal uses
        // E_min -1).
        answer.append(subnormal ?
            DoubleConsts.MIN_EXPONENT :
            Math.getExponent(d));
      }
      return answer.toString();
    }
  }

  /**
   * Returns a {@code Double} object holding the
   * {@code double} value represented by the argument string
   * {@code s}.
   *
   * <p>If {@code s} is {@code null}, then a
   * {@code NullPointerException} is thrown.
   *
   * <p>Leading and trailing whitespace characters in {@code s}
   * are ignored.  Whitespace is removed as if by the {@link
   * String#trim} method; that is, both ASCII space and control
   * characters are removed. The rest of {@code s} should
   * constitute a <i>FloatValue</i> as described by the lexical
   * syntax rules:
   *
   * <blockquote>
   * <dl>
   * <dt><i>FloatValue:</i>
   * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
   * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
   * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
   * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
   * <dd><i>SignedInteger</i>
   * </dl>
   *
   * <dl>
   * <dt><i>HexFloatingPointLiteral</i>:
   * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
   * </dl>
   *
   * <dl>
   * <dt><i>HexSignificand:</i>
   * <dd><i>HexNumeral</i>
   * <dd><i>HexNumeral</i> {@code .}
   * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
   * </i>{@code .}<i> HexDigits</i>
   * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
   * </i>{@code .} <i>HexDigits</i>
   * </dl>
   *
   * <dl>
   * <dt><i>BinaryExponent:</i>
   * <dd><i>BinaryExponentIndicator SignedInteger</i>
   * </dl>
   *
   * <dl>
   * <dt><i>BinaryExponentIndicator:</i>
   * <dd>{@code p}
   * <dd>{@code P}
   * </dl>
   *
   * </blockquote>
   *
   * where <i>Sign</i>, <i>FloatingPointLiteral</i>,
   * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and
   * <i>FloatTypeSuffix</i> are as defined in the lexical structure
   * sections of
   * <cite>The Java&trade; Language Specification</cite>,
   * except that underscores are not accepted between digits.
   * If {@code s} does not have the form of
   * a <i>FloatValue</i>, then a {@code NumberFormatException}
   * is thrown. Otherwise, {@code s} is regarded as
   * representing an exact decimal value in the usual
   * "computerized scientific notation" or as an exact
   * hexadecimal value; this exact numerical value is then
   * conceptually converted to an "infinitely precise"
   * binary value that is then rounded to type {@code double}
   * by the usual round-to-nearest rule of IEEE 754 floating-point
   * arithmetic, which includes preserving the sign of a zero
   * value.
   *
   * Note that the round-to-nearest rule also implies overflow and
   * underflow behaviour; if the exact value of {@code s} is large
   * enough in magnitude (greater than or equal to ({@link
   * #MAX_VALUE} + {@link Math#ulp(double) ulp(MAX_VALUE)}/2),
   * rounding to {@code double} will result in an infinity and if the
   * exact value of {@code s} is small enough in magnitude (less
   * than or equal to {@link #MIN_VALUE}/2), rounding to float will
   * result in a zero.
   *
   * Finally, after rounding a {@code Double} object representing
   * this {@code double} value is returned.
   *
   * <p> To interpret localized string representations of a
   * floating-point value, use subclasses of {@link
   * java.text.NumberFormat}.
   *
   * <p>Note that trailing format specifiers, specifiers that
   * determine the type of a floating-point literal
   * ({@code 1.0f} is a {@code float} value;
   * {@code 1.0d} is a {@code double} value), do
   * <em>not</em> influence the results of this method.  In other
   * words, the numerical value of the input string is converted
   * directly to the target floating-point type.  The two-step
   * sequence of conversions, string to {@code float} followed
   * by {@code float} to {@code double}, is <em>not</em>
   * equivalent to converting a string directly to
   * {@code double}. For example, the {@code float}
   * literal {@code 0.1f} is equal to the {@code double}
   * value {@code 0.10000000149011612}; the {@code float}
   * literal {@code 0.1f} represents a different numerical
   * value than the {@code double} literal
   * {@code 0.1}. (The numerical value 0.1 cannot be exactly
   * represented in a binary floating-point number.)
   *
   * <p>To avoid calling this method on an invalid string and having
   * a {@code NumberFormatException} be thrown, the regular
   * expression below can be used to screen the input string:
   *
   * <pre>{@code
   *  final String Digits     = "(\\p{Digit}+)";
   *  final String HexDigits  = "(\\p{XDigit}+)";
   *  // an exponent is 'e' or 'E' followed by an optionally
   *  // signed decimal integer.
   *  final String Exp        = "[eE][+-]?"+Digits;
   *  final String fpRegex    =
   *      ("[\\x00-\\x20]*"+  // Optional leading "whitespace"
   *       "[+-]?(" + // Optional sign character
   *       "NaN|" +           // "NaN" string
   *       "Infinity|" +      // "Infinity" string
   *
   *       // A decimal floating-point string representing a finite positive
   *       // number without a leading sign has at most five basic pieces:
   *       // Digits . Digits ExponentPart FloatTypeSuffix
   *       //
   *       // Since this method allows integer-only strings as input
   *       // in addition to strings of floating-point literals, the
   *       // two sub-patterns below are simplifications of the grammar
   *       // productions from section 3.10.2 of
   *       // The Java Language Specification.
   *
   *       // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
   *       "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
   *
   *       // . Digits ExponentPart_opt FloatTypeSuffix_opt
   *       "(\\.("+Digits+")("+Exp+")?)|"+
   *
   *       // Hexadecimal strings
   *       "((" +
   *        // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
   *        "(0[xX]" + HexDigits + "(\\.)?)|" +
   *
   *        // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
   *        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
   *
   *        ")[pP][+-]?" + Digits + "))" +
   *       "[fFdD]?))" +
   *       "[\\x00-\\x20]*");// Optional trailing "whitespace"
   *
   *  if (Pattern.matches(fpRegex, myString))
   *      Double.valueOf(myString); // Will not throw NumberFormatException
   *  else {
   *      // Perform suitable alternative action
   *  }
   * }</pre>
   *
   * @param s the string to be parsed.
   * @return a {@code Double} object holding the value represented by the {@code String} argument.
   * @throws NumberFormatException if the string does not contain a parsable number.
   */
  public static Double valueOf(String s) throws NumberFormatException {
    return new Double(parseDouble(s));
  }

  /**
   * Returns a {@code Double} instance representing the specified
   * {@code double} value.
   * If a new {@code Double} instance is not required, this method
   * should generally be used in preference to the constructor
   * {@link #Double(double)}, as this method is likely to yield
   * significantly better space and time performance by caching
   * frequently requested values.
   *
   * @param d a double value.
   * @return a {@code Double} instance representing {@code d}.
   * @since 1.5
   */
  public static Double valueOf(double d) {
    return new Double(d);
  }

  /**
   * Returns a new {@code double} initialized to the value
   * represented by the specified {@code String}, as performed
   * by the {@code valueOf} method of class
   * {@code Double}.
   *
   * @param s the string to be parsed.
   * @return the {@code double} value represented by the string argument.
   * @throws NullPointerException if the string is null
   * @throws NumberFormatException if the string does not contain a parsable {@code double}.
   * @see java.lang.Double#valueOf(String)
   * @since 1.2
   */
  public static double parseDouble(String s) throws NumberFormatException {
    return FloatingDecimal.parseDouble(s);
  }

  /**
   * Returns {@code true} if the specified number is a
   * Not-a-Number (NaN) value, {@code false} otherwise.
   *
   * @param v the value to be tested.
   * @return {@code true} if the value of the argument is NaN; {@code false} otherwise.
   */
  public static boolean isNaN(double v) {
    return (v != v);
  }

  /**
   * Returns {@code true} if the specified number is infinitely
   * large in magnitude, {@code false} otherwise.
   *
   * @param v the value to be tested.
   * @return {@code true} if the value of the argument is positive infinity or negative infinity;
   * {@code false} otherwise.
   */
  public static boolean isInfinite(double v) {
    return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
  }

  /**
   * Returns {@code true} if the argument is a finite floating-point
   * value; returns {@code false} otherwise (for NaN and infinity
   * arguments).
   *
   * @param d the {@code double} value to be tested
   * @return {@code true} if the argument is a finite floating-point value, {@code false} otherwise.
   * @since 1.8
   */
  public static boolean isFinite(double d) {
    return Math.abs(d) <= DoubleConsts.MAX_VALUE;
  }

  /**
   * The value of the Double.
   *
   * @serial
   */
  private final double value;

  /**
   * Constructs a newly allocated {@code Double} object that
   * represents the primitive {@code double} argument.
   *
   * @param value the value to be represented by the {@code Double}.
   */
  public Double(double value) {
    this.value = value;
  }

  /**
   * Constructs a newly allocated {@code Double} object that
   * represents the floating-point value of type {@code double}
   * represented by the string. The string is converted to a
   * {@code double} value as if by the {@code valueOf} method.
   *
   * @param s a string to be converted to a {@code Double}.
   * @throws NumberFormatException if the string does not contain a parsable number.
   * @see java.lang.Double#valueOf(java.lang.String)
   */
  public Double(String s) throws NumberFormatException {
    value = parseDouble(s);
  }

  /**
   * Returns {@code true} if this {@code Double} value is
   * a Not-a-Number (NaN), {@code false} otherwise.
   *
   * @return {@code true} if the value represented by this object is NaN; {@code false} otherwise.
   */
  public boolean isNaN() {
    return isNaN(value);
  }

  /**
   * Returns {@code true} if this {@code Double} value is
   * infinitely large in magnitude, {@code false} otherwise.
   *
   * @return {@code true} if the value represented by this object is positive infinity or negative
   * infinity; {@code false} otherwise.
   */
  public boolean isInfinite() {
    return isInfinite(value);
  }

  /**
   * Returns a string representation of this {@code Double} object.
   * The primitive {@code double} value represented by this
   * object is converted to a string exactly as if by the method
   * {@code toString} of one argument.
   *
   * @return a {@code String} representation of this object.
   * @see java.lang.Double#toString(double)
   */
  public String toString() {
    return toString(value);
  }

  /**
   * Returns the value of this {@code Double} as a {@code byte}
   * after a narrowing primitive conversion.
   *
   * @return the {@code double} value represented by this object converted to type {@code byte}
   * @jls 5.1.3 Narrowing Primitive Conversions
   * @since JDK1.1
   */
  public byte byteValue() {
    return (byte) value;
  }

  /**
   * Returns the value of this {@code Double} as a {@code short}
   * after a narrowing primitive conversion.
   *
   * @return the {@code double} value represented by this object converted to type {@code short}
   * @jls 5.1.3 Narrowing Primitive Conversions
   * @since JDK1.1
   */
  public short shortValue() {
    return (short) value;
  }

  /**
   * Returns the value of this {@code Double} as an {@code int}
   * after a narrowing primitive conversion.
   *
   * @return the {@code double} value represented by this object converted to type {@code int}
   * @jls 5.1.3 Narrowing Primitive Conversions
   */
  public int intValue() {
    return (int) value;
  }

  /**
   * Returns the value of this {@code Double} as a {@code long}
   * after a narrowing primitive conversion.
   *
   * @return the {@code double} value represented by this object converted to type {@code long}
   * @jls 5.1.3 Narrowing Primitive Conversions
   */
  public long longValue() {
    return (long) value;
  }

  /**
   * Returns the value of this {@code Double} as a {@code float}
   * after a narrowing primitive conversion.
   *
   * @return the {@code double} value represented by this object converted to type {@code float}
   * @jls 5.1.3 Narrowing Primitive Conversions
   * @since JDK1.0
   */
  public float floatValue() {
    return (float) value;
  }

  /**
   * Returns the {@code double} value of this {@code Double} object.
   *
   * @return the {@code double} value represented by this object
   */
  public double doubleValue() {
    return value;
  }

  /**
   * Returns a hash code for this {@code Double} object. The
   * result is the exclusive OR of the two halves of the
   * {@code long} integer bit representation, exactly as
   * produced by the method {@link #doubleToLongBits(double)}, of
   * the primitive {@code double} value represented by this
   * {@code Double} object. That is, the hash code is the value
   * of the expression:
   *
   * <blockquote>
   * {@code (int)(v^(v>>>32))}
   * </blockquote>
   *
   * where {@code v} is defined by:
   *
   * <blockquote>
   * {@code long v = Double.doubleToLongBits(this.doubleValue());}
   * </blockquote>
   *
   * @return a {@code hash code} value for this object.
   */
  @Override
  public int hashCode() {
    return Double.hashCode(value);
  }

  /**
   * Returns a hash code for a {@code double} value; compatible with
   * {@code Double.hashCode()}.
   *
   * @param value the value to hash
   * @return a hash code value for a {@code double} value.
   * @since 1.8
   */
  public static int hashCode(double value) {
    long bits = doubleToLongBits(value);
    return (int) (bits ^ (bits >>> 32));
  }

  /**
   * Compares this object against the specified object.  The result
   * is {@code true} if and only if the argument is not
   * {@code null} and is a {@code Double} object that
   * represents a {@code double} that has the same value as the
   * {@code double} represented by this object. For this
   * purpose, two {@code double} values are considered to be
   * the same if and only if the method {@link
   * #doubleToLongBits(double)} returns the identical
   * {@code long} value when applied to each.
   *
   * <p>Note that in most cases, for two instances of class
   * {@code Double}, {@code d1} and {@code d2}, the
   * value of {@code d1.equals(d2)} is {@code true} if and
   * only if
   *
   * <blockquote>
   * {@code d1.doubleValue() == d2.doubleValue()}
   * </blockquote>
   *
   * <p>also has the value {@code true}. However, there are two
   * exceptions:
   * <ul>
   * <li>If {@code d1} and {@code d2} both represent
   * {@code Double.NaN}, then the {@code equals} method
   * returns {@code true}, even though
   * {@code Double.NaN==Double.NaN} has the value
   * {@code false}.
   * <li>If {@code d1} represents {@code +0.0} while
   * {@code d2} represents {@code -0.0}, or vice versa,
   * the {@code equal} test has the value {@code false},
   * even though {@code +0.0==-0.0} has the value {@code true}.
   * </ul>
   * This definition allows hash tables to operate properly.
   *
   * @param obj the object to compare with.
   * @return {@code true} if the objects are the same; {@code false} otherwise.
   * @see java.lang.Double#doubleToLongBits(double)
   */
  public boolean equals(Object obj) {
    return (obj instanceof Double)
        && (doubleToLongBits(((Double) obj).value) ==
        doubleToLongBits(value));
  }

  /**
   * Returns a representation of the specified floating-point value
   * according to the IEEE 754 floating-point "double
   * format" bit layout.
   *
   * <p>Bit 63 (the bit that is selected by the mask
   * {@code 0x8000000000000000L}) represents the sign of the
   * floating-point number. Bits
   * 62-52 (the bits that are selected by the mask
   * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
   * (the bits that are selected by the mask
   * {@code 0x000fffffffffffffL}) represent the significand
   * (sometimes called the mantissa) of the floating-point number.
   *
   * <p>If the argument is positive infinity, the result is
   * {@code 0x7ff0000000000000L}.
   *
   * <p>If the argument is negative infinity, the result is
   * {@code 0xfff0000000000000L}.
   *
   * <p>If the argument is NaN, the result is
   * {@code 0x7ff8000000000000L}.
   *
   * <p>In all cases, the result is a {@code long} integer that, when
   * given to the {@link #longBitsToDouble(long)} method, will produce a
   * floating-point value the same as the argument to
   * {@code doubleToLongBits} (except all NaN values are
   * collapsed to a single "canonical" NaN value).
   *
   * @param value a {@code double} precision floating-point number.
   * @return the bits that represent the floating-point number.
   */
  public static long doubleToLongBits(double value) {
    long result = doubleToRawLongBits(value);
    // Check for NaN based on values of bit fields, maximum
    // exponent and nonzero significand.
    if (((result & DoubleConsts.EXP_BIT_MASK) ==
        DoubleConsts.EXP_BIT_MASK) &&
        (result & DoubleConsts.SIGNIF_BIT_MASK) != 0L) {
      result = 0x7ff8000000000000L;
    }
    return result;
  }

  /**
   * Returns a representation of the specified floating-point value
   * according to the IEEE 754 floating-point "double
   * format" bit layout, preserving Not-a-Number (NaN) values.
   *
   * <p>Bit 63 (the bit that is selected by the mask
   * {@code 0x8000000000000000L}) represents the sign of the
   * floating-point number. Bits
   * 62-52 (the bits that are selected by the mask
   * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
   * (the bits that are selected by the mask
   * {@code 0x000fffffffffffffL}) represent the significand
   * (sometimes called the mantissa) of the floating-point number.
   *
   * <p>If the argument is positive infinity, the result is
   * {@code 0x7ff0000000000000L}.
   *
   * <p>If the argument is negative infinity, the result is
   * {@code 0xfff0000000000000L}.
   *
   * <p>If the argument is NaN, the result is the {@code long}
   * integer representing the actual NaN value.  Unlike the
   * {@code doubleToLongBits} method,
   * {@code doubleToRawLongBits} does not collapse all the bit
   * patterns encoding a NaN to a single "canonical" NaN
   * value.
   *
   * <p>In all cases, the result is a {@code long} integer that,
   * when given to the {@link #longBitsToDouble(long)} method, will
   * produce a floating-point value the same as the argument to
   * {@code doubleToRawLongBits}.
   *
   * @param value a {@code double} precision floating-point number.
   * @return the bits that represent the floating-point number.
   * @since 1.3
   */
  public static native long doubleToRawLongBits(double value);

  /**
   * Returns the {@code double} value corresponding to a given
   * bit representation.
   * The argument is considered to be a representation of a
   * floating-point value according to the IEEE 754 floating-point
   * "double format" bit layout.
   *
   * <p>If the argument is {@code 0x7ff0000000000000L}, the result
   * is positive infinity.
   *
   * <p>If the argument is {@code 0xfff0000000000000L}, the result
   * is negative infinity.
   *
   * <p>If the argument is any value in the range
   * {@code 0x7ff0000000000001L} through
   * {@code 0x7fffffffffffffffL} or in the range
   * {@code 0xfff0000000000001L} through
   * {@code 0xffffffffffffffffL}, the result is a NaN.  No IEEE
   * 754 floating-point operation provided by Java can distinguish
   * between two NaN values of the same type with different bit
   * patterns.  Distinct values of NaN are only distinguishable by
   * use of the {@code Double.doubleToRawLongBits} method.
   *
   * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
   * values that can be computed from the argument:
   *
   * <blockquote><pre>{@code
   * int s = ((bits >> 63) == 0) ? 1 : -1;
   * int e = (int)((bits >> 52) & 0x7ffL);
   * long m = (e == 0) ?
   *                 (bits & 0xfffffffffffffL) << 1 :
   *                 (bits & 0xfffffffffffffL) | 0x10000000000000L;
   * }</pre></blockquote>
   *
   * Then the floating-point result equals the value of the mathematical
   * expression <i>s</i>&middot;<i>m</i>&middot;2<sup><i>e</i>-1075</sup>.
   *
   * <p>Note that this method may not be able to return a
   * {@code double} NaN with exactly same bit pattern as the
   * {@code long} argument.  IEEE 754 distinguishes between two
   * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>.  The
   * differences between the two kinds of NaN are generally not
   * visible in Java.  Arithmetic operations on signaling NaNs turn
   * them into quiet NaNs with a different, but often similar, bit
   * pattern.  However, on some processors merely copying a
   * signaling NaN also performs that conversion.  In particular,
   * copying a signaling NaN to return it to the calling method
   * may perform this conversion.  So {@code longBitsToDouble}
   * may not be able to return a {@code double} with a
   * signaling NaN bit pattern.  Consequently, for some
   * {@code long} values,
   * {@code doubleToRawLongBits(longBitsToDouble(start))} may
   * <i>not</i> equal {@code start}.  Moreover, which
   * particular bit patterns represent signaling NaNs is platform
   * dependent; although all NaN bit patterns, quiet or signaling,
   * must be in the NaN range identified above.
   *
   * @param bits any {@code long} integer.
   * @return the {@code double} floating-point value with the same bit pattern.
   */
  public static native double longBitsToDouble(long bits);

  /**
   * Compares two {@code Double} objects numerically.  There
   * are two ways in which comparisons performed by this method
   * differ from those performed by the Java language numerical
   * comparison operators ({@code <, <=, ==, >=, >})
   * when applied to primitive {@code double} values:
   * <ul><li>
   * {@code Double.NaN} is considered by this method
   * to be equal to itself and greater than all other
   * {@code double} values (including
   * {@code Double.POSITIVE_INFINITY}).
   * <li>
   * {@code 0.0d} is considered by this method to be greater
   * than {@code -0.0d}.
   * </ul>
   * This ensures that the <i>natural ordering</i> of
   * {@code Double} objects imposed by this method is <i>consistent
   * with equals</i>.
   *
   * @param anotherDouble the {@code Double} to be compared.
   * @return the value {@code 0} if {@code anotherDouble} is numerically equal to this {@code
   * Double}; a value less than {@code 0} if this {@code Double} is numerically less than {@code
   * anotherDouble}; and a value greater than {@code 0} if this {@code Double} is numerically
   * greater than {@code anotherDouble}.
   * @since 1.2
   */
  public int compareTo(Double anotherDouble) {
    return Double.compare(value, anotherDouble.value);
  }

  /**
   * Compares the two specified {@code double} values. The sign
   * of the integer value returned is the same as that of the
   * integer that would be returned by the call:
   * <pre>
   *    new Double(d1).compareTo(new Double(d2))
   * </pre>
   *
   * @param d1 the first {@code double} to compare
   * @param d2 the second {@code double} to compare
   * @return the value {@code 0} if {@code d1} is numerically equal to {@code d2}; a value less than
   * {@code 0} if {@code d1} is numerically less than {@code d2}; and a value greater than {@code 0}
   * if {@code d1} is numerically greater than {@code d2}.
   * @since 1.4
   */
  public static int compare(double d1, double d2) {
    if (d1 < d2) {
      return -1;           // Neither val is NaN, thisVal is smaller
    }
    if (d1 > d2) {
      return 1;            // Neither val is NaN, thisVal is larger
    }

    // Cannot use doubleToRawLongBits because of possibility of NaNs.
    long thisBits = Double.doubleToLongBits(d1);
    long anotherBits = Double.doubleToLongBits(d2);

    return (thisBits == anotherBits ? 0 : // Values are equal
        (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
            1));                          // (0.0, -0.0) or (NaN, !NaN)
  }

  /**
   * Adds two {@code double} values together as per the + operator.
   *
   * @param a the first operand
   * @param b the second operand
   * @return the sum of {@code a} and {@code b}
   * @jls 4.2.4 Floating-Point Operations
   * @see java.util.function.BinaryOperator
   * @since 1.8
   */
  public static double sum(double a, double b) {
    return a + b;
  }

  /**
   * Returns the greater of two {@code double} values
   * as if by calling {@link Math#max(double, double) Math.max}.
   *
   * @param a the first operand
   * @param b the second operand
   * @return the greater of {@code a} and {@code b}
   * @see java.util.function.BinaryOperator
   * @since 1.8
   */
  public static double max(double a, double b) {
    return Math.max(a, b);
  }

  /**
   * Returns the smaller of two {@code double} values
   * as if by calling {@link Math#min(double, double) Math.min}.
   *
   * @param a the first operand
   * @param b the second operand
   * @return the smaller of {@code a} and {@code b}.
   * @see java.util.function.BinaryOperator
   * @since 1.8
   */
  public static double min(double a, double b) {
    return Math.min(a, b);
  }

  /**
   * use serialVersionUID from JDK 1.0.2 for interoperability
   */
  private static final long serialVersionUID = -9172774392245257468L;
}
